A checkout system includes a workstation having a data capture arrangement for capturing through a horizontal window a target associated with a product to identify the product being checked out at the workstation, and a scale for weighing the product at the workstation. It is characterized by automatically running demonstration programs when it is supplied with electric power but is left unattended at a store or in an exhibition area. These observations are utilized by a collaborative blame attribution algorithm to identify a suspect network entity that caused the Web transaction failure. Upon receipt of a plurality of bids from sellers, a buyer can then select a seller-supplier based at least in part on the price schedule.